Treatment of hydrocarbons



June 19, 1934. 1 LAWRENCE 1,963,092

TREATMENT OF HYDROCARBONS Fild May 25, 1955 Inventor FranlIinILLammPatented June 19, 1934 UNITED STATES PATENT OFFICE TREATMENT OFHYDROCARBONS Franklin I. L. Lawrence, Philadelphia, Pa., as-

signor to The Atlantic Refining Company, Philadelphia, Pa., acorporation of Pennsylvama Application May 25, 1933, Serial No. 672,821

17 Claims.

This invention relates to a process of cracking and polymerizinghydrocarbons, under suitable conditions of temperature and pressure, toconvert the same into polymers, which include and products such as tarand fixed gases, e. g., methane mation of the least amount of tar andfixed gas,

and thereafter separating the aromatic products from the tar andunreacted low boiling hydrocarbons.

I have found that the operating conditions most 3: suitable foreffecting eflicient cracking and polymerization vary with the particularhydrocarbons undergoing treatment, e. g., ethane, requires a much highercracking temperature to form unsaturated compounds which will polymerizethan 40 do the higher boiling hydrocarbons, as propane and butane. Ingeneral, the greater the number of carbon atoms in the compound, theless drastic is the treatment necessary to decompose it, particularlywith the view of forming unsaturated hydrocarbons.

I separate the gaseous-hydrocarbons into fractions according to boilingpoint and subject the several fractions in a unitary system to thoseconditions most suitable for the maximum production of the desiredpolymers. In carrying on my process, a mixture of low boilinghydrocarbons, such as comprises refinery or pressure still gas, issubjected to compression in one or more stages, preferably with partialreboiling of the condensate and partial condensation of the vapors, andfractionation of the gas to cause a separation into fractions varyingaccording to their respective boiling points.

It will be evident from Table I, that the different hydrocarbon groupsmay be separated substantially from each other, the variance in theboiling ranges of the C2, C3, and C4 hydrocarbons and the fixed gasesmaking such fractionation feasible.

Table I Propane Assuming the charging gas to contain hydrogen, methane,ethane and ethylene, propane and propylene, and butanes and butylenes,the liquid formed in the first stage of a three stage compression systempreferably will beprimarily hydrocarbons of the C4 type, i. e., butaneand buty-,- lenes; in the second stage the Ca hydrocarbons, and in thethird stage the C2 hydrocarbons. If only two stages are used the C:hydrocarbons may appear in either or both of the other fractions,depending uponthe operating conditions. Hydrogen, methane, and otherfixed gases which remain unliquefied in the operation, will be conductedfrom the system as gas.

As hereinafter explained, one or more of the liquid fractions thusobtained are passed into their respective heating or cracking coils, theC: hydrocarbon fraction being heated to a sufficient temperature and fora suflicient time to secure the maximum conversion to olefines withoutexcessive formation of secondary decomposition products, as fixed gasand tar. The heater for the C2 hydrocarbons is preferably operated at atemperature of from 1150 F. to 1400 F'., the heater for the C3hydrocarbons from about 400 F. to 800 F., and for the C4 hydrocarbons avariable temperature up to but usually not exceeding 800 F. However, itis tobe understood that the temperatures maintained in the respectiveheat-' ers may be varied according to the type and amount ofhydrocarbons introduced, the pressure under which the system may beoperated, and the time of exposure of the gases to the operatingtemperature. The time'of exposure is generally less than one minute,although in the lower temperature ranges the time may be somewhat lessthan seconds. I prefer to operate the heating and polymerization systemsat a pressure of 5 from 100 lbs. to 1000 lbs/sq. in., and morepreferably at from 100 lbs. to 500 lbs/sq. in. However, my process maybe operated at pressures up to 2000 lbs/Sq. in.

After the endothermic formation of the unsaturated hydrocarbons from theC2 fraction by the high temperature treatment, the gases are cooled bythe addition of the C3 and/ or C4 hydrocarbon fraction, said C3 and/orC4 fraction being heated as above stated or to a lesser degree or beingin an unheated condition, and are introduced into an unheated reactionchamber wherein simul- 1150 F. to 1200 F. most preferred. I preferablyeffect the cooling of the products of the heating step by addingcondensate from'an earlier stage of compression, i. e., the C3 and/orthe C4 hydro carbon fraction, this condensate added thus being raised toa suitable temperature for cracking and/or polymerization of theconstituents thereof to form relatively low boiling aromatic or cyclichydrocarbons. The liquids used for the cooling stepmay, if necessary, bepreheated in their respective heaters in order to insure the propertemperature during the cracking and/or polymerization step.

The products withdrawn from the reaction chamber may be separated intolow boiling aromatic compounds suitable as motor fuel, higher boilingreaction products such as tar, recycle gas, and vent gas, as hydrogenand methane. I may effect the separation by cooling the treated materialwithdrawn from the reaction chamber to a temperature which causescondensation of components of higher boiling range than the desiredliquid polymers, removing such condensate from the system andfractionating under pressure the polymers from the unreactedhydrocarbons and fixed gas. I prefer to carry out this fractionationunder such conditions that hydrogen, methane and other undesirable gasesare withdrawn from the fractionating column as gas, while theunpolymerized hydrocarbons containing 2, 3, or 4 carbon atoms to themolecule may be removed as liquids and recycled for further cracking andpolymerization. I contemplate the removal of one or more side-streams ofliquefied gas, the said stream or streams thus removed preferably beingadded to the corresponding fractions from the initial compressionoperation. The liquefied gas streams withdrawn from the fractionatingcolumn may be subjected to a stripping or reboiling operation to effecta further separation of the constituents before the same are recycled.

When more than two liquids fractions are to be treated, it may bedesirable to'preheat the higher boiling one and pass it through only aportion of the reaction chamber, introducing it at an intermediatepoint, thereby reducing the time of exposure to the elevatedtemperature.

My invention may be further understood by reference to the accompanyingdrawing which illustrates diagrammatically apparatus suitable foreffecting my treatment.

Refinery or pressure still gas is introduced into the system thru pipe1, partially liquefied by compressor 2, cooled in heat exchanger 3 andpassed into the fractionating column 4, provided with heating coil 7 andcooling coil 8. 'Assuming the gas charged to be a mixture of hydrogen,methane and C2, C3 and C4 hydrocarbons, the hydrogen, methane and C2compounds are withdrawn from .the top of the column 4 and passed thrupipes 20 and 22 into compressor 23, being compressed therein and passedthru pipe 24 and cooler 25, into fractionating column 26, provided withheating coil '7 and cooling coil 8. The fixed gases, hydrogen andmethane are withdrawn from the top of column 26, thru pipe 27 and areremoved from the system. The C2 hydrocarbons are drawn from the bottomofcolumn 26 through pipe 38 and are forced by pump 39 thru valve 40 andpipe 41 into heatingcoil 42, under a pressure of 100- 1000 lbs./sq.in.,wherein such hydrocarbons are heated to a temperature of from 1150 F. to1400 F., to efiect cracking of the C2 hydrocarbons to form unsaturatedcompounds such as ethylene, together with some methane and hydrogen.

From the middle of column 4 there is withdrawn the C3 hydrocarbonfraction, which is passed thru pipe 1'7 into the reboiler 18 where anyC2 or lighter hydrocarbons are stripped and returned thru pipe 19 tocolumn 4. The fraction withdrawn from the bottom of column 18 iscomposed of substantially the C3 hydrocarbons. This material is passedthrough pipe 31, pump 32, valve 33, and pipe 34 into heating coil 35under a pressure of from approximately 100 to 1000 lbs/sq. in., andtherein is heated to a temperature of the order or from 400 F. to 800F., with substantially no cracking taking place.

The fraction removed from the bottom of column 4, comprisingsubstantially the C4 hydrocarbons, passes thru pipe 5, pump 6, valve 9,and pipe 10 into heating coil 11, and is raised to a temperature notexceeding 800 F., while under a pressure of the order or from about 100to 1000 lbs./ sq. in., wherein preheating of the C4 hydrocarbons isaccomplished without substantial decomposition. The products from theheating coil 11 are withdrawn thru pipe 12, and are then either passedby valve 14 into pipe 37 to be admixed with the products from coil 35,and then to the reaction chamber 16, or passed through valve 13 and pipe15 into the unheated reaction chamber 16. The heated products from coil35 are passed thru pipe 36, valve 44, pipe 37, and thence into thereaction chamber at the same point of introduction as the products fromcoil 42 passed thereinto through .pipe 43. The C4 hydrocarbons from thebottom of column 4 may be passed directly to the reaction chamber 16through pipe 10 and valve controlled by-pass 9', said fraction beingcracked and polymerized by the contained heat of the gases present inthe reaction chamber 16. The C3 hydrocarbons from the bottom of tower 18may. likewise be by-passed directly from pipe 34 through valve 33, pipe36,

valve 44 and pipe 37 into pipe 43 and thence.

into the reaction chamber 16.

The reaction chamber 16, in which a major portion of the polymerizationof unsaturates to aromatics occurs is maintained by the heated gasesintroduced thereinto, at a temperature of from about 1150" F. to 1200 F.and at substantially the same pressure as the heating coils, i. e., 100to 1000 lbs/sq. in. The products from the three heating coils 11, 35,and 42, after polymerization in the reaction chamber 16 are withdrawnthrough. pipe 45, cooler 46, valve 4'7 and pipe 48, into a tar strippingcolumn 49. The heavy polymers, in the form of tar are fractionated outand removed from the bottom of the column thru pipe 50 and valve 51. Thedesired low boiling aromatic polymers, together with any unreacted C2,C3 and C4 hydrocarbons as well as hydrogen and methane, are withdrawn asvapors from the top of column 49 and passed through pipe 52 into thefractionating column 53 intermediate its top and bottom. Therein afractionation under. pressure is effected, the aromatic polymers beingremoved from the bottom of the column through pipe 54 and valve 55.

The heaviest side stream, comprising for the most part the C4hydrocarbons, is withdrawn through pipe 56 and valve 57 into a reboilercolumn 58 wherein a further fractionation is accomplished, any C3hydrocarbons or lighter being removed from the top of the column throughpipe 59 and returned to column 53. The C4 compounds are drawn from thebottom of the reboiler 58 through pipe 60, and are forced by pump 61,through valve 62, pipe 63, valves 64 and 65, into pipe 10 for recyclingto the heater 11.

Similarly, a second side stream is taken from column 53, through pipe 68and valve 69 into reboiler 70. This stream comprises mainly the C3hydrocarbons, but also contains some of the C2 and lighter compounds,the same being withdrawn from the top of reboiler '70 through pipe '72and returned to column 53. The liquid drawn from the bottom of thereboiler 70, substantially the C3 hydrocarbons, passes through pipe 71,pump 73, valve '74, pipe '75, valves '76 and 77, into pipe 34 forrecycling to heater 35.

The lightest side stream, other than the fixed gases, is withdrawn fromcolumn 53 through pipe '78 and valve '79 and passed into reboiler 80.This stream comprises substantially all of the C2 hydrocarbons, togetherwith some gaseous methane and hydrogen. The fixed gases are removed fromthe top of reboiler through pipe 82 and are returned to column 53. TheC2 hydrocarbons are drawn from the bottom of 80 through pipe 81, and arepassed by means of pump 83, thru valve 84, pipe 85, valves 86 and 8'7,into pipe 41 for recycling to heater 42.

The remaining fixed gases, as hydrogen and methane are withdrawn fromthe top of column 53 through pipe 88 and may either be discharged fromthe system through valve 28 and pipe 2'7 or if they still have admixedtherewith substantial amounts of materials having boiling points higherthan methane, they may be recycled through the fractionating system. Therecycling may be accomplished either by closing valve 28 and passing thegases thru valve 29, pipe 30 and valve-controlled by-pass 24a intocooler 25 and column 26, the valves 21 and 21a being closed, or thegases may be passed from pipe 88 thru valve 29, valve28 being closed,thence thru pipe 30 and valve controlled by-pass 21 into cooler 3 andcolumn 4, the valves 24a and 21a being closed.

The side streams taken from column 53, may, by regulation of pumps 61,'73, and 83, and valves 66, 6'7, 86, '76, and 64, be diverted from theirnormal course of flow into any desired heater, or a mixture of two ormore side streams may be recycled to any particular heater.

It may be desirable to operate my process so that the Ca and C4hydrocarbons are segregated as a group and are preheated together in thesame heater, the C2 hydrocarbons being separated and cracked accordingto the normal procedure described hereinbefore. In such case, the C3 andC4 fractions are removed from the bottom of column 4, the column 18being cut out of the system by closing valves 17a' and 19a. The C3-C4mixture withdrawn from column 4 through pipe 5 is passed by pump 6through valve 9, and pipe 10 into heater 11 and thence by means of pipe12, valve 14, pipe 3'7, and valve 44 into reaction chamber 16. The C2hydrocarbon fraction, following its normal passage from the bottom ofcolumn 26, is passed through heater 42 and thence into reaction chamberv16 wherein the cracking and/or polymerization of the gases occurs;

While the foregoing description of my processillustrates the treatmentof only three hydrocarbon fractions, namely C2, C3 and C4 compounds,additional fractions may be obtained from each stage of compression byremoving side streams of intermediate boiling range between thecondensate removed from the bottom of the fractionating column 4 and thevapor leaving the top. It is preferable to subject such side streams toa stripping or reboiling operation to remove low boiling componentspresent therein, and the revaporized portion may be returned to thefractionating tower or otherwise disposed of. Whn several fractions arethus obtained from a single stage of compression, they may each besubjected to the particular treatment-which will produce the maximumyield of desirable polymers.

Also, while the accompanying drawing illustrates the separation of thecharging gas into fractions by means of fractionating columns oper atingunder elevated pressures, I contemplate the use of any fractionatingmeans, such as for example, asystem of absorption whereby the componentsof the charging gas are selectively absorbed in oil or other medium andthe absorbed gas fractions either along with the absorbent or strippedfrom the absorbent are subjected to thermal treatment according to myprocess. Furthermore, the time of cracking and of polymerization, andthe temperatures and pressures required may be varied considerably fromthose given by way of illustration, depending upon the character of thehydrocarbons undergoing treatment and the polymers desired.

In carrying out my process upon certain gaseous mixtures, it may befound advantageous or desirable from an economic or other standpoint, toobtain polymers, for example, from only the C3 and the higher fractions.In such cases the system would be operated so that the lower fractions,for instance, the C2 fraction would not be subjected to cracking andpolymerization, but would, for example, be conducted from the systemalong with the fixed gases, whereupon at least two of the remainingfractions would each be subjected to that thermal treatment best suitedfor its cracking and/or polymerization. This and similar variations arewithin the scope of my invention.

In the appended claims, there are claims limited to a species of myinvention, as well as broader claims'which in addition to covering suchspecies, also cover another or other species. In my copendingapplication, Serial No. 717,086, filed March 28, 1934, there are claimslimited to another or other species or modifications therein disclosedand broader claims covering additional species.

Herein, and in the appended claims "C2, C3, and C4 hydrocarbons are tobe understood to comprehend ethane and ethylene, propane and propylene,and butanes and butylenes, respectively. Likewise, the term aromatichydrocarbons is to be understood to comprehend the hydro-aromatic orhydro-cyclic compounds such as cyclohexane and cyclo-hexene, as well asthe true aromatic hydrocarbons such asbenzene, toluene, and similarhomologues.

What I claim is:

The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydro-- carbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing at least two of the fractions under apressure greater than atmospheric, separately heating one of saidcompressed fractions to a temperature at which said fraction willdecompose to form substantial quantities of unsaturated hydrocarbons,introducing the heated fraction andanother of said compressed fractionsinto a reaction zone wherein formation of polymers occurs, and removingthe products of reaction from the zone last mentioned.

2. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressuregreater than atmospheric, separately heating at least one of saidcompressed fractions to a temperture at which said fraction willdecompose to form substantial quantities of unsaturated hydrocarbons,introducing a fraction so heated and at least one other of the saidcompressed fractions into a reaction zone wherein formation of polymersoccurs, removing the products of reaction from the zone last mentioned,and separating the liquid aromatic polymers therefrom.

3. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressuregreater than atmospheric separately heating at least one of thecompressed fractions to a temperature at which the fraction willdecompose to form substantial quantities of unsaturated hydrocarbons,introducing the heated fraction and at least one other of the compressedfractions into a reaction zone wherein formation of polymers occurs,removing the prodnets of reaction from the zone last mentioned,fractionally separating the reaction products into a tar fraction, anaromatic polymer fraction, and unpolymerized hydrocarbon fractions ofsuccessively lower boiling range,'and recycling an unpclymerizedhydrocarbon fraction for further heat treatment.

4. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a pluralityrof the-fractions to a pressuregreaterthan atmospheric, separately heating each of the compressedfractions, introducing the heated gases into a reaction zone whereinformation of polymers occurs, removing the products of reaction from thezone last mentioned, and separating the liquid aromatic polymerstherefrom.

5. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressuregreater than atmospheric, separately heating each of the compressedfractions, introducing the heated gases into a reaction zone whereinformation of polymers occurs, removing the products of reaction from thezone last mentioned, fractionally separating the said reaction productsinto a tar fraction, an aromatic polymer fraction, and unpolymerizedhydrocarbon fractions of successively lower boiling ranges, andreturning at least one of the said unpolymerized hydrocarbon fractions,under pressure, to its respective heating zone.

6. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressureof the order of from about 100 lbs. to about 2000 lbs/sq. in.,separately heating the lowest boiling compressed hydrocarbon fraction toa temperature of the order of from about 1150 F. to about 1400 F.,whereby'decomposition is effected and substantial quantities ofunsaturated hydrocarbons are formed, introducing the heated gaseousproducts and at least one other of the said compressed fractions into areaction zone at a temperature of the order of from about 950 to about1300 F., wherein formation of polymers occurs, removing the products ofreaction from the zone last mentioned, and separating the liquidaromatlc polymers therefrom.

7. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressureof the order of from about '100 lbs. to about 1000 lbs/sq. in.,separately heating the lowest boiling compressed hydrocarbon fraction toa temperature of from about 1150 F. to about 1400 F., wherebydecomposition is effected and substantial quantities of unsaturatedhydrocarbons are formed, introducing the heated gaseous products and atleast one of the other of the said compressed fractions into a reactionzone at a temperature of the order of from about 950 F. to about 1300F., wherein formation of polymers occurs, removing the products ofreaction from the zone last mentioned, and separating the liquidaromatic polymers therefrom.

8. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowermolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressureof the order of from about 100 to about 500 lbs/sq. in., separatelyheating the lowest boiling compressed hydrocarbon fraction to atemperature of the order of from about 1150 F. to about 1400 F., wherebydecomposition is effected and substantial quantities of unsaturatedhydrocarbons are formed, introducing the heated gaseous products and atleast one of the compressed fractions into a reaction zone at atemperature of the order of from about 950 F. to about 1300 F., whereinformation of polymers occurs, removing the products of reaction from thezone last mentioned, and separating the liquid aromatic polymerstherefrom.

9. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, compressing a plurality of the fractions to a pressureof the order of from about 100 to 2000 lbs/sq. in., separately heatingthe lowest boiling compressed hydrocarbon fraction to a temperature ofthe order of from about 1150 F. to about 1400 F., whereby decompositionis effected and substantial quantities of unsaturated hydrocarbons areformed, introducing the heated gaseous products and at least one of thecompressed fractions into a reaction zone at a temperature of the orderof from about 950 F. to about 1300 F., wherein formation of polymersoccurs, removing the products 0' reaction from the zone last mentioned,fractionally separating the reaction products into a tar fraction, anaromatic polymer fraction, and unpolymerized hydrocarbon fractions ofsuccessively lower boiling ranges, and recycling at least one of theunpolymerized hydrocarbon fractions for further heat treatment.

10. The process for obtaining liquid aro-, matic polymers from lowmolecular weight gaseous mixtures containing C2, C3 and C4 hydrocarbons,methane and fixed gases, which comprises separating the gaseous mixtureinto fractions containing substantially C2, C3 -and C4 hydrocarbonsrespectively, compressing a plurality of the fractions to a pressuregreater than atmospheric, separately heating at least one of saidcompressed fractions .to a temperature at which said fraction willdecompose to form substantial quantities of unsaturated hydrocarbons,introducing the heated fraction and at least one other of the saidcompressed fractions into a reaction zone wherein formation of polymersoccurs, removing the products of reaction from the zone last mentioned,and separating the liquid aromatic polymers therefrom.

11. The process for obtaining liquid aromatic polymers from lowmolecular weight gaseous mixtures containing C2, C3, and C4hydrocarbons, 4

methane and fixed gases, which comprises separating the gaseous mixtureinto fractions containing substantially C2, C3, and C4 hydrocarbonsrespectively, compressing a plurality of the fractions to a pressuregreater than atmospheric, separately heating at least one of the saidcompressed fractions to a temperature at which said fraction willdecompose to form substantial quantities of unsaturated hydrocarbons,introducing the heated fraction and at least one other of the saidcompressed fractions into a reaction zone wherein the formation ofpolymers occurs, removing the products of the reaction from the zonelast mentioned, fractionally separating the said reaction products intoa tar fraction, an aromatic polymer fraction, and unpolymerizedhydrocarbon fractions containing substantially C2, C3 and C4hydrocarbons respectively, and recycling at least one of the saidunpolymerized fractions for further heat treatment.

12. The process for obtaining liquid aromatic polymers from lowmolecular weight gaseous mixtures containing C2, C3, and C4hydrocarbons, methane and fixed gases, which comprises separating thegaseous mixture into fractions containing substantially Ca, Ca, and C4hydrocarbons respectively, compressing each of the said fractions to apressure of the order of from about 100 to about 2000 lbs/sq. in.,separately heating the C2 hydrocarbon fraction to a temperature of theorder of from about 1150 F. to about 1400 F., the C3 hydrocarbonfraction to .a temperature of the order of from about 400 F. to 800 F.,and the C4 hydrocarbon fraction to a temperature not exceedingsubstantially 800 F., introducing the compressed heated gases into areaction zone at a temperature of the order of from about 950 F. toabout 1300 F., wherein formation of polymers occurs, removing theproductsof reaction from the zone last mentioned, and separating theliquid aromatic polymers therefrom.

13. The process for obtaining liquid aromatic polymers from lowmolecular weight gaseous mixtures containing C2, C3, and C4hydrocarbons, methane and fixed gases, which comprises separating thegaseous mixture into fractions containing substantially the C2, C3, andC4 hydrocarbons respectively, compressing each of the said fractions toa pressure of the order of from about .100 to 1000 lbs./sq. in.,separately heating the C:

hydrocarbon fraction to a temperature of the order of from about 1150 F.to about 1400 F., the Ca hydrocarbon fraction to a temperature of theorder of from about 400 F. to about 800 F., and the C4 hydrocarbonfraction to a temperature not exceeding substantially 800 F.,introducing the compressed heated gases into a reaction zone at atemperature of the order of from about 950 F. to about 1300 F., whereinformation of polymers occurs, removing products of reaction from thezone last mentioned, and separating the liquid aromatic polymerstherefrom.

14. The process for obtaining liquid aromatic polymers from lowmolecular weight gaseous mixture containing C2, C3, and C4 hydrocarbons,methane and fixed gases, which comprises separating the gaseous mixtureinto fractions containing substantially the C2, C3, and C4 hydrocarbonsrespectively, compressing each of the said fractions to a pressure ofthe order of about 100 to 500.lbs. /sq. in., separately heating the C2hydrocarbon fraction to a temperature of the order of from about 1150 F.to about 1400 F.,

the C3 hydrocarbon fraction to a temperature of,

the order of from about 400 F. to about 800 F.,

and the C4 hydrocarbon fraction to a temperature not exceedingsubstantially 800 F., introducing the compressed heated gases into areaction zone at a temperature of the order or from about- 950 F. toabout 1300 F., wherein formation of polymers occurs, removing theproducts of reaction from the zone last mentioned, and separating theliquid aromatic polymers therefrom. v

15. The process for obtaining liquid aromatic polymers from lowmolecular weight gaseous mixtures containing Ca, Ca and C4 hydrocarbons,methane and fixed gases, which comprises separating the gaseous mixtureinto fractions containing substantially the C2, C3, and C4 hydrocarbonsrespectively, compressing each of the said fractions to a pressure ofthe order of from about 100 to 2000 lbs/sq. in., separately heating theC2 hydrocarbon fraction to a temperature of the order of from about 1150F. to about 1400 F., the C3 hydrocarbon fraction to a temperature of theorder of from about 400 F. to about 800 F., and the C4 hydrocarbonfraction to a temreaction zone at a temperature of the order of fromabout 950 F. to about 1300 F., wherein formation of polymers occurs,removing the products of reaction from the zone last mentioned,fractionally separating the said reaction products into a tar fraction,an aromatic polymer fraction, and unpolymerized C2, C3 and C4hydrocarbon fractions, and returning at least one of the saidunpolymerized hydrocarbon fractions, under pressure, toits respectiveheating zone.

. 16. The process for obtaining liquid aromatic hydrocarbons from lowmolecular weight hydrocarbons, which comprises separating the lowmolecular weight hydrocarbons into fractions of successively lowerboiling ranges, heating at least one of the fractions so separated to atemperature at which said fraction will decompose to sub-v stantialextent to form unsaturated hydrocar bons, introducing the heatedfraction and at least one other of the fractions into a reaction zonewherein formation of polymers occurs. removing the products of reactionfrom the zone last mentioned, separating polymers therefrom, andrecycling at least a portion of the unpolymerized materials. I

17. The process for. converting low molecular weight hydrocarbons intopolymers, which comprises first compressing the hydrocarbons, thenseparating them into fractions of successively lower boiling ranges,heating one or more of said fractions under superatmospheric pressure toa temperature at which portions thereof will decompose to formunsaturated hydrocarbons, bringing the heated fraction into contact withanother compressed fraction to efiect formation of polymers, andthereafter effecting a separation of the polymers.

FRANKLIN r. L. LAWRENCE.

